1. Field of the Invention
The invention relates to a method for recovering oil from an oil-bearing formation and more particularly relates to a method for recovering oil in which the oil is displaced from the formation by injecting a solution of a normally solid polymerized methacrylate such as an acetone solution of polymethyl methacrylate, and recovering the oil thus displaced from the formation.
2. Description of the Prior Art
Oil is normally recovered from subterranean formations in which it has accumulated by penetrating said formation with one or more wells and pumping or permitting the oil to flow to the surface through these wells. Recovery of oil from oil containing formations is possible only if certain conditions are satisfied. There must be an adequate concentration of oil in the formation, and there must be sufficient porosity and permeability or interconnected flow channel throughout the formation to permit the flow of fluids therethrough if sufficient pressure is applied to the fluid. When the subterranean petroleum containing formation has natural energy present in the form of an underlying active water drive, or gas dissolved in the petroleum which can exert sufficient pressure to drive the oil to the producing well, or a high pressure gas cap above the oil within the oil reservoir, this natural energy is utilized to recover oil. Recovery of oil by utilization of natural energy is referred to as primary recovery. When this natural energy source is depleted, or in the instance of those formations which do not originally contain sufficient natural energy to permit primary recovery operations, some form of supplemental recovery process must be utilized in order to extract oil from the subterranean petroleum containing formation. Supplemental recovery is frequently referred to as secondary recovery, although in fact it may be primary, secondary or tertiary in sequence of employment.
Water flooding, which involves the injection of water into the subterranean oil-bearing formation for the purpose of displacing oil toward the producing well, is the most economical and widely practiced supplemental recovery method. Water does not displace oil with high efficiency, however, since water and oil are immersible, and also because the interfacial tension between water and oil is quite high.
Another problem faced by those attempting to improve the efficiency of the water flood by the addition of hydrophilic polymeric materials has been the tendency of such polymer solutions to channel and to move prefrentially through portions of the formation which have been waterflooded and which are now essentially waterflooded. There is a definite need in the art for displacement fluids which will prevent such channeling effects.